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    SubjectRe: [RFC PATCH 4/4] [PATCH 4/4] mm: add tracing for VMA merges
    On Fri, 18 Feb 2022 13:20:19 +0100
    Jakub Matěna <matenajakub@gmail.com> wrote:

    > diff --git a/include/trace/events/mmap.h b/include/trace/events/mmap.h
    > index 4661f7ba07c0..9f6439e2ed2d 100644
    > --- a/include/trace/events/mmap.h
    > +++ b/include/trace/events/mmap.h
    > @@ -6,6 +6,7 @@
    > #define _TRACE_MMAP_H
    >
    > #include <linux/tracepoint.h>
    > +#include <../mm/internal.h>
    >
    > TRACE_EVENT(vm_unmapped_area,
    >
    > @@ -42,6 +43,60 @@ TRACE_EVENT(vm_unmapped_area,
    > __entry->low_limit, __entry->high_limit, __entry->align_mask,
    > __entry->align_offset)
    > );
    > +
    > +TRACE_EVENT(vm_av_merge,
    > +
    > + TP_PROTO(int merged, enum vma_merge_res merge_prev, enum vma_merge_res merge_next, enum vma_merge_res merge_both),
    > +
    > + TP_ARGS(merged, merge_prev, merge_next, merge_both),
    > +
    > + TP_STRUCT__entry(
    > + __field(int, merged)
    > + __field(enum vma_merge_res, predecessor_different_av)
    > + __field(enum vma_merge_res, successor_different_av)
    > + __field(enum vma_merge_res, predecessor_with_successor_different_av)
    > + __field(int, diff_count)
    > + __field(int, failed_count)
    > + ),
    > +
    > + TP_fast_assign(
    > + __entry->merged = merged == 0;
    > + __entry->predecessor_different_av = merge_prev;
    > + __entry->successor_different_av = merge_next;
    > + __entry->predecessor_with_successor_different_av = merge_both;
    > + __entry->diff_count = (merge_prev == AV_MERGE_DIFFERENT)
    > + + (merge_next == AV_MERGE_DIFFERENT) + (merge_both == AV_MERGE_DIFFERENT);
    > + __entry->failed_count = (merge_prev == AV_MERGE_FAILED)
    > + + (merge_next == AV_MERGE_FAILED) + (merge_both == AV_MERGE_FAILED);

    Please indent the above better. That is:

    __entry->diff_count = (merge_prev == AV_MERGE_DIFFERENT)
    + (merge_next == AV_MERGE_DIFFERENT)
    + (merge_both == AV_MERGE_DIFFERENT);


    > + ),
    > +
    > + TP_printk("merged=%d predecessor=%d successor=%d predecessor_with_successor=%d diff_count=%d failed_count=%d\n",
    > + __entry->merged,
    > + __entry->predecessor_different_av, __entry->successor_different_av,
    > + __entry->predecessor_with_successor_different_av,
    > + __entry->diff_count, __entry->failed_count)

    To make the above easier to read for humans, you could have at the start:

    #define AV_MERGE_TYPES \
    EM(MERGE_FAILED), \
    EM(AV_MERGE_FAILED) \
    EM(MERGE_OK) \
    EMe(AV_MERGE_DIFFERENT)

    #define EM(a) TRACE_DEFINE_ENUM(a);
    #define EMe(a) TRACE_DEFINE_ENUM(a);

    AV_MERGE_TYPES

    #undef EM
    #undef EMe

    #define EM(a) {a, #a},
    #define EMe(a) {a, #a}

    Then:

    TP_printk("merged=%d predecessor=%s successor=%s predecessor_with_successor=%s diff_count=%d failed_count=%d",

    (note, no "\n", get rid of that)

    __entry->merged,
    __print_symbolic(predecessor_different_av, AV_MERGE_TYPES),
    __print_symbolic(successor_different_av, AV_MERGE_TYPES),
    __print_symbolic(predecessor_with_successor_different_av, AV_MERGE_TYPES),
    __entry->diff_count, __entry->failed_count)

    Then the output will show strings instead of meaningless numbers.

    -- Steve


    > +
    > +);
    > +
    > +TRACE_EVENT(vm_pgoff_merge,
    > +
    > + TP_PROTO(struct vm_area_struct *vma, bool anon_pgoff_updated),
    > +
    > + TP_ARGS(vma, anon_pgoff_updated),
    > +
    > + TP_STRUCT__entry(
    > + __field(bool, faulted)
    > + __field(bool, updated)
    > + ),
    > +
    > + TP_fast_assign(
    > + __entry->faulted = vma->anon_vma;
    > + __entry->updated = anon_pgoff_updated;
    > + ),
    > +
    > + TP_printk("faulted=%d updated=%d\n",
    > + __entry->faulted, __entry->updated)
    > +);
    > #endif
    >
    > /* This part must be outside protection */

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